Being Helpful, Creepy

If you live in a major urban area, do your part to keep the neighborhood safe. Leave post-it notes on apartment doors with subtle reminders to the importance of proper security.

One suggestion: "Your front door was open. Thought you should know. I borrowed sugar." Do not sign your name. Good Samaritans want recognition; great ones don't.

The owner of the apartment will be confused, and possibly weirded out, but certainly more security-conscious.